[Bug c/42907] New: -fstrict-aliasing breaks valid code

["fejj at novell dot com" <gcc-bugzilla at gcc dot gnu dot org>]

When compiling the attached C code with gcc 4.4.1 [gcc-4_4-branch revision
150839] w/ -O2 -fstrict-aliasing, gcc outputs broken machine code.

>From what I can gather by stepping thru the generated program with gdb, gcc has
dropped a number of statements that are required for the code to properly
function. For example, it has dropped:

- the initialization of list
- the initialization of tail
- the updating of the tail pointer after each iteration thru the loop (if you
pretend like gcc didn't unroll the loop)
- the comparison of list to NULL after the loop

I'll also attach my gdb session.


-- 
           Summary: -fstrict-aliasing breaks valid code
           Product: gcc
           Version: 4.4.1
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: fejj at novell dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42907